i have a 1/4 scale nosen aeronca champ with scale items on it, it has a u.s. 41 gas engine in it, questions are: whats the scale size prop for this plane.?

whats the largest prop a 41 can swing for scale flight?

I just got back from the field and a member had a us 41 swinging an 18x10 Xoar on a 1/4 scale super decathlon.(98" WS). It did fine with that prop on it. I know some people really like a scale prop escpecially on a contest plane but, very rarely due they actually fly with a scale prop. At least from what I've seen. They are mostly just for staitic display. Look at most of the warbirds for example. During static display they all have beautiful 4 and 3 blade hamilton's hanging on them. But, when they fire the engine up for flying they have a 2 blade wood or carbon fiber that is best suited for the engine they have chosen.
I would guess that something in the 17 -19" range would be a scale size. Just my .02
P.S. Xoar makes some good looking painted props that might fit your need, I believe they are called swords.

My Champ is over powered with a Brison 2.4 swingining a Zinger 18 X 10. The scale is about 1/4.5. Dan.

I had a Quadra 42 (same as US 41) on a 16.5 lb. Giant Sportster for a while. It had what I would describe as "great" sport performance on an APC 20x8w.

For scale performance, you could probably go up to a 22x6, depending on what the plane weighs?

The 18 X10 is the standard prop that everyone uses on the US41/Quadra42 engines

On a Cub there's not reason a 19 X 8 or 20 X 8 couldn't be used.

Everyone? Granted, an 18x10 will load the engine properly, but why would you want to run something with that amount of pitch on Champ/Cub type plane (kite)? Not like a plane like this is going to be running as fast as a warbird or something... why not give it the benefit of having some extra punch at lower speeds if you could? Flatter pitch also usefull in controlling speeds on downlines? I'm just not seeing an upside to 10" of pitch, but maybe I'm missing something.

I was just commenting on the fact that the 41 I saw handled the 18x10 fine and gave the Super Decathlon that it was on good get up and go. I have never owned or flew a plane that had one on the front. They seem to be pretty reliable engines from what I have heard about them. They look to be a little on the heavy side but some folks like fatties. I do agree that if it swings an 18x10 than it should do alright with an 19x8 or maybe even a 20x6. Back to the original ?, I don't know what would be a scale sized prop on your plane. You might have to take clearance issues into account as well.

I've been around a lot of 1/4 scale Cubs and Robinhood 99's with US 41 and Quadra 42 engines. They all ran 18 X 10 props and all looked correct and performed fine. but there's no reason the other props could not be used.

Hi

Looking for any info on the Quadra engines, parts, specs, suggestions on why I can't get a spark.
I think that it is a 42cc<br type="_moz"/>

you will find a 20x8 will work very well too.

Do you have a shut off switch installed on it? Does it have points? Have you tried a new plug?

No points, it is of a magneto type ignition, yes it had a cut off switch, plug is not the problem.

Do we know anyone that repairs these engines?  

if it is a magneto engine, you will not get much if any spark flipping it by hand. A spring starter will turn it fast enough to get a bright blue spark. If the plug is good and you are getting no spark using a spring start, it is probably the ignition module. Note that the modules seldom fail. You have provided little in information about what you are doing to start and check the engine.

I'm lame!

I pulled the plug out and used an electric starter, still no spark, and yes I had the plug grounded.
Do you know what the gap should be between the magnets on the flywheel and the ignition face should be?
At this time it is about .020 thou.

Thanks for your imput, I am all ears.

Chris

The magneto gap is right, a US 41 mag engine will hand start easily...take the ground switch wire completely off at the coil....

Ground wire is/was off.  With an ohm meter I checked to see if the coil had a short, that is negative, no short.
I reset the gap between the magnets and the coil to .014 . . . . . . . NO CHANGE, NO SPARK!

I have fourteen hairs left which one should I pull?

I couldn't find specs on the full scale prop, but the Champ was designed to compete with the Piper Cub (J3), and as the Cub uses a 72" prop, my guess is that the Champ does similarly. That would scale down to 18" @25%. Your engine is probably capable of turning a larger prop, so experimenting with which prop flies best will be a fun exercise.
Good luck .